Conventionally, a rolling bearing assembly has been widely used for rotatably carrying a wheel under a body of an automotive vehicle. As shown in FIG. 6, such a bearing assembly generally includes: an outer ring member 233 fixed to the vehicle body and possessing double raceway surfaces formed on an inside surface thereof; an inner ring member 235 located radially inwardly of the outer ring member 233 in a coaxial relation therewith and adapted for rotation as possessing double raceway surfaces formed on an outside surface thereof; and two rows of rolling elements 236 rollably interposed between the raceway surfaces of the outer ring member 233 and the inner ring member 235. The inner ring member 235 includes: a hub spindle 237; and an inner-ring component member 238 independent from the hub spindle 237 and fitted on a vehicular-inner-side end of the hub spindle 237. In cases, a cover 245 may be fitted in a vehicular-inner-side end of the outer ring member 233 such as to prevent muddy water and the like from entering a radially inside area of the outer ring member through a vehicular-inner-side opening thereof. A sensor for detecting the number of revolutions of the wheel is normally mounted to the cover in a case where the control of an antilock brake system or a traction control system is provided.
Such a cover 245 has conventionally been formed from a metal material by using a mold. More recently, however, it has become a practice to form the cover 254 from a synthetic-resin material in order to reduce the weight and cost thereof (see, for example, Japanese Unexamined Patent Publication No. 2004-44664).
Because of the material properties, the synthetic-resin cover 245 per se cannot achieve a great fitting or engaging force. Therefore, an arrangement is contemplated wherein a core 247 substantially having a short cylindrical shape is provided on an inside surface of a cover portion, which is fitted in the inside surface of the outer ring member, so that the cover may achieve a predetermined fitting or engaging force based on the rigidity of the core 247 (FIG. 7).
During manufacture of the cover, the core 247 is placed at a predetermined position in a mold so as to be unified with the cover 245. Since the synthetic-resin material forming the cover 245 and the metal forming the core 247 have different linear expansion coefficients, repeated temperature fluctuations may cause the core 247 to disengage from the cover 245 and to project to a vehicular outer side (indicated by a hollow arrow in FIG. 7). If the core 247 disengages from the cover 245, the cover 245 is decreased in the fitting or engaging force so that the cover 245 may be displaced from a predetermined position with respect to the outer ring member 233. What is worse, the cover may disengage from the outer ring member 233. In such cases, the sensor mounted to the cover 245 is displaced so as to be unable to detect the number of revolutions of the wheel correctly. This disables the control of the antilock brake system or the like. Furthermore, the disengaged core 247 may interfere with another component, producing noises or causing damage thereto. If the cover 245 disengages from the outer ring member, the muddy water and the like may enter the radially inside area of the outer ring member 233 and may corrode the components of the bearing assembly.
In view of the foregoing, the invention has an object to provide a bearing assembly adapted to prevent the core used with the synthetic-resin cover from disengaging from the cover.